Metal, sulfur and nitrogen removal from hydrocarbons utilizing moving-bed reactors

ABSTRACT

Hydroprocessing of hydrocarbon charge stocks which contain sulfur and various metals is performed using two moving-bed reactors connected in series; intermittently fresh catalyst is added to and used catalyst is removed from the second reactor, the used catalyst is regenerated and charged to the first reactor for use in metals removal and initial hydrotreating of the charge stock.

United States Patent 1 1 Adams et a1.

1*Aug. 19, 1975 METAL, SULFUR AND NITROGEN REMOVAL FROM HYDROCARBONS[56] References Cited UTILIZING MOVING-BED REACTORS UNITED STATESPATENTS Inventors: Frank R Adams; Robert F 2,684,930 7/1954 Berg 208/216Anderson, both of Lagrange Park, 2,956,004 10/1960 Conn et a1. 208/251 HIll. 3,795,607 3/1974 Adams et al. 208/210 Asslgneez ggl g f g g CPrimary ExaminerDelbert E. Gantz Assistant ExaminerG. J. CrasanakisNotice: The portion of the term of this Attorney, Agent, or Firm lamesR. Hoatson, Jr.;

p n subsequent to 1991, Robert W. Erickson; William H. Page, II has beendisclaimed.

Filed: on. 24, 1973 ABSTRACT Hydroprocessing of hydrocarbon chargestocks which contain sulfur and various metals is performed using twomoving-bed reactors connected in series; intermittently fresh catalystis added to and used catalyst is removed from the second reactor, theused catalyst is regenerated and charged to the first reactor for use inAppl. No.: 409,216

Related US. Application Data Continuation-impart of Ser. No. 282,999,Aug. 23, 1972, Patv No. 3,795,607.

-S- l- 208/251 208/254 H metals removal and initial hydrotreating of thecharge Int. Cl. Cl0g 23/08 tock Field Of Search 208/209, 211, 213, 210,

7 5 4 Claims, 1 Drawing Figure Recycle H Char e Stack Amine Reactor 28CanIac/a!\ Re actor 25 To Praducr Separationl '/4 J Lac/r Happe/ LackHopper Separator Spent (.a/a/ys/ Ta 1 Metal: Recavery Regeneration ZonePATENTEU AUG 1 9 1975 Recycle H Charge Rea c/or Sfoc'k Look Hopper Am/le20 i 28 l 'Conracror\ [26 L Reactor 25 8 Separator /6 l l /e 24 3 LightHydrocarbons l7 3 i [/8 8 Lac/r Hopper Separa/or Spent Ca/a/ys/ To lMeta/s Recovery 7'0 Pro do of Separation? Regeneration Zone [HopperMETAL, SULFUR AND NITROGEN REMOVAL FROM HYDROCARBONS UTILIZINGMOVING-BED REACTORS CROSS REFERENCE TO RELATED APPLICATION Thisapplication is a continuation-in-part of our copending application, Ser.No. 282,999, filed Aug. 23, 1972, which issued as U.S. Pat. No.3,795,607 on Mar. 5, 1974, all the teachings of which copendingapplication are incorporated herein by specific reference thereto.

BACKGROUND OF THE INVENTION 1. Field of the Invention The inventionpertains to the hydrotreating and hydrorefining of hydrocarbons toremove metals, sulfur, and nitrogen and to the hydrocracking ofhydrocarbons. Optimal usage of a catalyst being fouled by metalsdeposition is achieved through continuous operation of moving-bedreactors with transfer of regenerated catalyst between reactors beforeit is discarded. Regeneration of the catalyst is accomplished by burningoff carbon, followed by optional reduction and sulfiding of the basemetal on the catalyst prior to use.

2. Description of the Prior Art The advantages of a moving-bed system invapor phase reforming operations are described in U.S. Pat. Nos.3,470,090 and 3,647,680, and various catalyst transferring routes aredescribed in U.S. Pat. No. 2,370,234. In another group of references,U.S. Pat. Nos. 3,607,725; 3,679,574 and 3,686,093, the catalyst movesthrough fluidized reaction zones countercurrently to the feed andhydrogen in the performance of hydrocracking and metals removaloperations. A recently disclosed moving-bed desulfurization process ispresented in U.S. Pat. No. 3,730,880.

Processing hydrocarbons by passage with hydrogen over beds of catalystis described in detail in the prior art. Specific examples are U.S. Pat.No. 2,767,121 which teaches the manner in which a naphtha boiling rangecharge stock is treated for sulfur and nitrogen removal and to saturateolefins in the preparation of charge stock for a catalytic reformingunit. In U.S. Pat. No. 2,717,857, a process for the desulfurization ofgas oil fractions (material boiling over 400F., the normal end point forgasoline) is discussed. Heavy oil hydrotreating processes and techniquesare also described in U.S. Pat. Nos. 3,501,396; 3,471,397; 3,371,029;3,375,189 and 3,429,801. A catalyst especially useful for thehydrorefining of heavy residual oil is described, along with a processusing the catalyst, in US. Pat. No. 3,525,684.

Processes for the purposes outlined above have tradi tionally beenperformed using a fixed bed of catalyst contained in one or morereaction vessels. This procedure has two inherent disadvantages tooperation which it is the object of this invention to remove. As thecatalyst in a fixed bed system is used, its activity gradually decreasesand results in a continued lessening in the quality of the productunless the reaction conditions are modified. Second, when it is nolonger possible to maintain adequate product quality, the catalyticmaterial must be replaced while processing is switched to another swingreactor or while the process is not operating. The catalyticdesulfurization of residual fuel oils is hindered by fouling of thecatalyst by coke, metals removed from the oil, salt, scale and otherplant trash. In addition to reducing the activity of the catalyst,deposits of such material increase the pressure drop in the reactorresulting in higher operating expenses and interfere with the uniformdistribution of hydrogen and oil across the catalyst, thereby causingchanneling, hot spots and further catalyst deactivation. Shut downs dueto these problems are very costly due to the loss of production andcatalyst replacement expense. A technique resorted to in the prior artto avoid this problem is the use of guard reactors prior to the maindesulfurization reactor. These reactors are used on a swing basis,meaning only one is in the process flow at any time while the other isbeing regenerated or refilled with new catalyst. In the processing ofcrude oils containing a high concentration of metals, the deactivationof the catalyst due to the metal content of the oil is as serious aproblem as deactivation due to carbon deposition on the catalyst eventhough it may occur at a slower rate. The regeneration of the catalystby burning off the carbon does not result in a full restoration of thecatalytic activity of the catalyst since the metals are not removed. Itis an object of this invention to provide a means whereby hydrotreatingof a metalcontaining residual crude oil can be performed on a continuousbasis, with catalyst being circulated from a second reaction zone to afirst reaction zone and then discarded when completely spent. In thismanner, metals removed in the guard reactor and particulate materialfiltered out in the guard reactor are not admitted to the main, second,reaction zone.

SUMMARY OF THE INVENTION l-lydrotreating is accomplished in a tworeactor moving-bed system using series flow of the charge stock and twostep reverse series flow of the catalyst between reactors to provideinitial metals removal and clean up of the charge stock in the firstreactor containing the regenerated used catalyst and the remainder ofthe hydrotreating in the second reactor containing the fresh catalyst.The process comprises the steps of passing the hydrocarbon charge stockand hydrogen through the first moving-bed reaction zone containingregenerated catalyst, passing some effluent from the first reaction zonethrough the second reaction zone containing fresh catalyst, whileintermittently removing used catalyst from the bottom of the secondreaction zone, separating this used catalyst from the effluent of saidsecond reaction zone, contacting the used catalyst with anoxygen-containing gas to burn off accumulated carbon deposits to therebyregenerate the catalyst, and passing said regenerated catalyst into thefirst reaction zone from which spent catalyst is sent to a metalsrecovery unit.

DESCRIPTION OF THE DRAWING Hydrocarbon charge stock and hydrogen enterthe process through line 1 located at the top of the first reactor 2 andpass downward through the reactor to exit by line 3 and transfer into aseparator 18. Light vaporous material is removed from the separator vialine 19, and the partially processed charge stock leaves by line 20 forpassage to the second reactor 4. Fresh makeup hydrogen from line 22 andpurified hydrogen from line 29 are added via line 21 before thepartially processed charge stock enters the second reactor 4. The lightvaporous material leaving by line 19 is cooled by means not shown andpassed into a high pressure separator 23.

Liquefied light hydrocarbons are removed from the separator via line 24and a hydrogenrich vapor is removed via line 25. This vapor is passedinto a vaporliquid contactor 26. An amine or caustic solution enters thecontactor via line 28 and removes H S from the hydrogen-rich gasentering through line 25. Spent amine solution leaves the contactorthrough line 27 and a purified hydrogen stream leaves via line 29 to becharged to reactor 4. Hydrotreated products leave the process by line 5for passage to a second high pressure separator or other processing asmay be appropriate.

Fresh catalyst is fed to the system through line 6 by means of lockhopper 7 used to equalize pressure on the catalyst before admission tosecond reactor 4. This catalyst gradually travels downward through thereactor and, as used catalyst, is removed from the bottom of the reactorthrough means 8 and fed into lock hopper 9. The separated catalyticmaterial is then transported through line 10 into regeneration zone 11located in a second lock hopper wherein the catalyst is contacted withan oxygen-containing gas such as air which enters by a means not shown.After suitable carbon removal by oxidation has occurred in theregeneration zone, catalytic material is first passed by line 12 intohopper l3 and then pressurized through line 14 to the lock hopper 15located at the top of the first reactor. Catalyst added to the firstreactor 2 through lock hopper l5 flows downward through the reactorwherein initial metals removal from the charge stock is performed andextraneous particulate matter is removed. Spent catalyst is removedthrough means 16 and enters lock hopper 17 for removal from the reactorsystem and passage to a metals recovery unit. For the purpose of clarityand simplicity, controls, valves, heat exchangers, and other equipmentobviously necessary have not been shown. The drawing and thisdescription of the drawing are not intended to in any way limit themanner in which the process may be utilized. The re generation zone maycomprise a fluidized bed, a moving-bed similar to the reaction zone, ora fixed bed as previously indicated. Additional steps such as reductionand sulfiding of the catalyst prior to its return to a reaction zone arewithin the scope of this invention. Reduction and sulfiding can beconducted in the transfer line 14 or in lock hopper 15 or within thesecond reaction vessel itself.

DETAILED DESCRIPTION OF THE INVENTION The broad field of hydroprocessingis divided into three main subdivisions. The first is hydrotreatingwherein materials such as sulfur, nitrogen, and metals contained invarious organic molecular structures are removed from the charge stockwith very little molecular cracking. The second subdivision ishydrocracking, wherein at least 50% of the charge stock is cracked intosmaller molecular weight components, such as the production of a naphthafrom a heavy distillate. Hydrorefining is between these two extremes andresults in molecular changes to up to 10% of the feed together withimpurity removal. Although there are many differences in processingconditions or suitable catalysts and flow schemes for these twodifferent operations, they are basically alike in most aspects.

The catalysts used in these processes are typically composed of a basemetal, which is defined to be a metal selected from the group comprisingnickel, iron, and cobalt, supported on an inorganic oxide carrier.

The manufacture and composition of these catalysts is an an in itselfand is not directly relevant to the practice of the process of thisinvention. A typical catalyst may contain from about 0.1 to 10% nickelor other metal or a combination of metals from the base metal group,along with other metals such as molybdenum or vanadium. The basematerial of the catalyst will normally be a refractory inorganic oxidesuch as alumina, silica, zirconia, boria, etc. or combinations of any ofthese materials, particularly, alumina in combination with one or moreof the other oxides. The alumina is usually in excess with a weightratio of alumina to other components of from 1.5:1 to about 9:1 andpreferably from about 1.5:] to about 3:1. The inclusion of a smallamount of silica is very common to increase the overall crackingactivity of the catalyst since silica itself is an effective crackingcatalyst even though used as a support for the metals. Details ofproduction of suitable catalysts are given in US. Pat. No. 3,525,684.

Processing conditions for any hydrorefining operation are determined bythe charge stock, the catalyst used and the desired result of theprocess. A broad range of conditions include a temperature of from 500F.to 1000F., a pressure of from 300 psig. to 4000 psig., and a liquidhourly space velocity of 0.5 to about 5.0. The liquid hourly spacevelocity is defined as the volume of the liquid charged to the reactordivided by the volume of the catalyst in the reactor. The exact reactortemperature required is determined by the activity and age of thecatalyst. As a general rule, the operating pressure will be increasedwith the boiling point of the material being processed. In allhydrotreating operations, hydrogen is circulated through the process ata rate of from about 1000 to about 25,000 standard cubic feet per barrelof charge. This is to increase vaporization and thereby improveprocessing results, to provide hydrogen for the formation of ammonia andhydrogen sulfide from the nitrogen and sulfur removed from the chargestock, and for the saturation of olefinic hydrocarbons and crackinglarge molecules. The production of hydrogen sulfide and ammonia makes itnecessary to in some manner remove these compounds from the process on acontinuous basis. Normal procedure to accomplish this is the injectionof water into the reactor effluent to dissolve the salts of theseimpurities followed by cooling sufficient to form a water phase which isdecanted from a separatory vessel. A second method is the treatment ofthe hydrogen recycle stream with a caustic solution to scrub out the H8. The performance of these and other suitable operations is well knownto those skilled in the art and warrants no further explanation.

In the processing of residual fractions of crude petroleum, it is commonthat metals, most commonly nickel and vanadium, will be present in thisfraction at concentrations exceeding ppm. by weight. These metals are animpurity that must be removed prior to further processing or use of thecrude oil. This is commonly done in the same process in which the sulfurand nitrogen are removed by hydrocracking the large metal containing andusually thermally stable molecules to break free the individual metalatoms. The metal released in this manner accumulates on the catalyst andwill cause its eventual deactivation, and during a cycle of catalyst usecan be as serious a problem as the deactivation caused by carbondisposition on the catalyst due to coking of the charged hydrocarbonmaterial.

Metals deposited on the catalyst in this manner are not removed by theburning off of the built up carbon layers making it impossible toregenerate the used catalyst to an activity equal to that of unusedcatalyst. Eventual replacement of used catalyst is a very time consumingprocedure which the present invention eliminates.

Catalysts are also fouled by salt, scale, plant trash and particulateimpurities contained in the residual fuel oil. It is therefore apparentthat the initial catalyst acts not only as a catalyst but also as afilter medium for the charged material. This phenomenon causesinterference with the uniform distribution of hydrogen and oil acrossthe catalyst bed resulting in channeling of reactant flow, hot spots,and further catalyst deactivation. An increased pressure drop throughthe reactor which increases the expense of operation is also anundesirable result of this filter action. Shut downs due to theseproblems are very costly in both down time and catalyst replacementexpense. A technique for overcoming these disadvantages of the fixed bedmethods used in the prior art is a direct object of this invention.

The flow utilized in the present invention is series flow of the chargestock through two reactors with catalyst movement in a two stepsemi-countercurrent fashion wherein the fresh charge stock is firstcontacted with regenerated used catalyst. Catalyst movement is bygravity and therefore confined to a downward flow. Full countercurrentflow of the reactants in a liquid phase is seldom used inhydroprocessing of heavy oils because of the poor conversions andincreased catalyst deactivation rates which result. However,countercurrent vaporized oil flow, though hard to accomplish with heavyoils, would be desirable. The benefits of this moving-bed system includelonger process runs between shutdowns, dictated only by mechanicalproblems or periodic maintenance, the elimination of pressure drop buildup, a more consistent product and the ability to remove contaminants toa lower level with an equal amount of catalyst.

The invention comprises using regenerated catalyst in a first moving-bedreactor which is of small volume and serves as a guard reactor for themain moving-bed hydrotreating reactor of the process which used freshcatalyst. For this discussion, a moving-bed reactor is defined as areactor wherein a non-fluidized bed of catalyst is slowly transferredfrom one end of the reactor to the other end, in flow similar to plugflow of reactants, by the addition of catalyst at the first end andremoval at the second. New catalyst is charged to the top of the main,second, reactor and after a residence period determined by deactivationeffects present in both reactors, is removed from the bottom of thereactor and regenerated. The regeneration process is meant to be theremoval of built up layers of coke from the catalyst. Secondary optionalsteps associated with this regeneration are the reduction of the basemetal atoms contained on the catalyst from an oxidized state resultingfrom the combustion necessary to remove carbon, and the sulfiding ofthese metal atoms to reduce the cracking tendency of the raw metals.Although cracking is often desired in the process, the raw metals have anear uncontrollable catalytic activity which results in poor processingresults. The regenerated catalyst is then fed into the first reactor foruse as the initial cracking catalyst and as a filter medium. Spentcatalyst is withdrawn from the bottom of this first reaction zone andsent to a metals recovery unit or simply disposed of.

The deposition of carbon on the catalyst may cause deactivation at ahigher rate than the fouling of the catalyst by the accumulation ofmetals removed from the charged material. In this situation, theeconomic factors of process performance and catalyst cost may dietatethat regeneration of used catalyst from the second reactor be performedat a rate greater than the total degradation rate in the first reactor.Some portions of the regenerated catalyst would therefore be returned tothe second reactor rather than charged to the first reactor. This rateof catalyst return would be set by the relative deactivation rates andthe desired average activity of the two beds of catalyst which areinterrelated to such factors as utility expense, processing conditions,the average catalyst life, the catalyst turnover rate in the firstreactor and the relative physical size of the two reactors. Thecomplexity of these relationships makes it impossible in this discussionto describe an optimum catalyst turnover or recycle rate untilconstrained to a specific catalyst, charge stock, product specification,and reactor size.

The reverse of the above situation occurs when the rate of catalystfouling by metals deposition is very severe compared to carbon build up.To maintain the desired catalyst activity in the first reactor, it maybe necessary to charge fresh catalyst to both the first and secondreactors.

Recycling of catalyst removed from the first reactor to the firstreactor after regeneration may be appropriate in the special instancesof the start up of the process with both reactors loaded with freshcatalyst or with very excessive coke build up in the first reactor.

The addition and removal of catalysts from the reaction zones isperformed in a lock hopper type apparatus comprising an enclosed volumebetween two valves. In the addition step, catalyst from above is allowedto fall into the lock hopper, the top valve is closed, the pressure inthe lock hopper is equalized with the reaction zone and the bottom valveis then opened. In this manner, catalyst can be intermittently added to,and removed from, either reactor without upsetting the process due tochanges in the pressure or temperature of the reaction zone.

A lock hopper type device may also be used as the regeneration zonebetween the two reactors. in operation, catalyst would enter theregeneration zone which would then be sealed off, entrained oil removedand an oxygen containing gas would be passed over the catalyst which dueto its high temperature would spontaneously ignite and burn offhydrocarbon residue and coke layers. The temperature of the catalystbeing regenerated should not be allowed to exceed 850F. to 900F.Undesirable flash flame effects and resulting high temperatures areavoided by the judicious use of nitrogen purges of the lock hopperbefore regeneration, and the dilution of the air used in theregeneration by nitrogen or recycled combustion gases. The oxygenconcentration of the gas used to regenerate the catalyst is normallymaintained below about I to 2%.

After the regeneration process, the metal contained on the catalyst isin a highly oxidized state. The catalyst can be fed directly into thefirst reactor at this point. It is desirable, however, to perform thereduction and sulfiding gradually at controlled conditions and rateswhich produce an increased catalytic activity over that obtained by thedirect insertion of the catalyst into a reaction zone. The reduction canbe performed by passing a gas such as hydrogen or methane over thecatalyst at an elevated temperature to utilize the oxygen combined withmetal in a combustion process. After this step, the catalyst would becontacted with a sulfur containing substance such as hydrogen sulfide ora sulfur containing light cycle oil. US. Pat. No. 3,642,613 presents animproved method for reduction and sulfiding of fresh catalyst with aninitial prewetting with a light cycle oil for an extended period ofabout 18 hours while at a moderate temperature of about 300F., apressure of 2000 psig. and a hydrogen circulation rate of 5000 scf./Bbl.Following this, the temperature is raised to 450F. for a period of about32 hours or until an equilibrium concentration of H 8 is formed. Thecharge stock is then cut into the process, the light cycle oilcirculation is discontinued and the reactor is raised to the temperaturenecessary to perform the desired hydrotreating. In the presentinvention, the charge stock would of course not be contacted with thecatalyst until it had been transferred to the reaction zone. The methodof sulfiding chosen is dependent on the in crease in activity derivedcompared to the increased costs and the comparative rates ofdeactivation due to metals and coke disposition.

In some instances, it is desirable to perform a separation operation onthe first reactors effluent before charging it to a second reactor. Thismay be because the degree of cracking or treating performed on thelighter petroleum fractions of the charge stock renders any furthercatalytic contact unnecessary or undesirable. Processes in which suchseparation operations are performed are described in U.S. Pat. Nos.3,429,801; 3,471 ,397 and 3,501,396 which were first presented in theprior art section. Whether a separation operation is desirable willdepend on the degree to which the first reactor functions solely as ahigh severity guard reactor.

The most desirable flow path for the hydrogen utilized in this processmay differ from the serial flow of the hydrocarbon stream. This flowpath would be determined by an attempt to optimize the efficiency of theprocess by better control of the hydrogen and hydrogen sulfideconcentrations in the reactors. In a multipass conversion system, it isdesired to have a higher hydrogen purity and lower hydrogen sulfideconcentration in the final clean-up stage. To accomplish this, hydrogenand light gases are withdrawn from the effluent of a first reactor andpurified. The purification may comprise a partial condensation of thehydrocarbons followed by passage of the remaining gaseous materialthrough an absorption zone. An amine or caustic solution is usuallyemployed to remove hydrogen sulfide. The purified hydrogen stream formedin this manner and preferably also the make-up hydrogen are then addedto the hydrocarbon feed stream to the next reactor. The effluent streamof the last reactor is also separated for the recovery of hydrogen. Thishydrogen stream is then recirculated for use in the guard reactor or afirst reactor wherein hydrogen purity is not as critical and highersulfur levels may be more easily tolerated. This is the type of flowpath depicted in the drawing.

Although the hydrogen purification step is shown in the drawing asoccurring between the guard reactor and the second reactor of atwo-reactor process, our

invention is not so limited. There may for instance be three reactorswith the hydrogen separation being performed between the last two in thesequence. This may be the optimum case when the hydrogen sulfideconcentration of the hydrogen stream is raised by only a relativelysmall amount in its passage through the guard reactor. Further still,the effluent of one reactor may be split into two separate hydrocarbonfractions which are further hydroprocessed in separate reactors operatedat different severity factors including different space velocities ortemperatures.

Our invention may be described as a process for the catalytichydroprocessing of hydrocarbons containing metal, sulfur and nitrogenimpurities therein, said process which comprises the steps of: (a)passing a hydrocarbon charge stock and hydrogen through a firstmoving-bed reaction zone to contact regenerated catalyst hereinafterdescribed, said catalyst flowing downward in said first reaction zone toremove metal impurities from said charge stock; (b) passing at least aportion of the reaction efiluent from the first reaction zone to the topof a second moving-bed reaction zone to contact therein fresh catalystflowing downward in said second reaction zone to remove sulfur andnitrogen impurities from said effluent; (c) removing used catalyst fromthe bottom of said second reaction zone; ((1) contacting said usedcatalyst with an oxygen-containing gas in a regeneration zone to burnoff accumulated carbon deposits to form regenerated catalyst; (e)passing regenerated catalyst formed in step ((1) into said firstreaction zone as said regenerated catalyst of step (a); and, (f)withdrawing used catalyst from the bottom of said first reaction zone.

We claim as our invention:

1. A process for the catalytic hydroprocessing of hydrocarbonscontaining metal, sulfur and nitrogen impurities therein, said processhaving at least two movingbed reactors operated with series hydrocarbonflow which comprises the steps of:

a. passing a hydrocarbon charge stock and hydrogen through a firstmoving-bed reaction zone to contact regenerated catalyst hereinafterdescribed, said catalyst flowing downward in said first reaction zone toremove metal impurities from said charge stock;

. passing a portion of the reaction effluent from the first reactionzone to the top of a second movingbed reaction zone to contact thereinfresh catalyst flowing downward in said second reaction zone to removesulfur and nitrogen impurities from said ef fluent;

c. removing used catalyst from the bottom of said second reaction zone;

(1. contacting said used catalyst with an oxygencontaining gas in aregeneration zone to burn off accumulated carbon deposits to formregenerated catalyst;

e. passing regenerated catalyst formed in step (d) into said firstreaction zone as said regenerated catalyst of step (a); and,

f. withdrawing said regenerated catalyst containing said metalimpurities from the bottom of said first reaction zone.

2. A process for the catalytic hydroprocessing of hydrocarbonscontaining metal, sulfur and nitrogen impu rities therein, said processhaving at least two movingbed reactors operated with series hydrocarbonflow which comprises the steps of:

passing a hydrocarbon charge stock and hydrogen through a firstmoving-bed reaction zone to contact regenerated catalyst hereinafterdescribed, said catalyst flowing downward in said first reaction zone toremove metal impurities from said charge stock;

b. passing a portion of the reaction effluent from the d. contactingsaid used catalyst with an oxygencontaining gas in a regeneration zoneto burn off accumulated carbon deposits to form regenerated catalyst;

. passing regenerated catalyst formed in step (d) into said firstreaction zone as said regenerated catalyst of step (a); and,

withdrawing spent catalyst from the bottom of said first reaction zone.

3. A process for the catalytic hydroprocessing of hydrocarbonscontaining metal, sulfur and nitrogen impurities therein, said processusing at least two movingbed reactors operated in series hydrocarbonflow, which comprises the steps of:

a. passing a hydrocarbon charge stock and hydrogen through a firstmoving-bed reaction zone to contact regenerated catalyst hereinafterdescribed, said catalyst flowing downward in said first reaction zone toremove metal impurities from said charge stock;

b. passing a portion of the reaction effluent from the first reactionzone to the top of a second movingbed reaction zone to contact therein amixture of fresh and regenerated catalyst flowing downward in saidsecond reaction zone to remove sulfur and nitrogen impurities from saideffluent;

c. removing used catalyst from the bottom of said second reaction zone;

d. contacting said used catalyst with an oxygencontaining gas to burnoff accumulated carbon deposits to form regenerated catalyst in aregeneration zone;

e. passing a portion of said regenerated catalyst formed in step (d)into said first reaction zone as said regenerated catalyst of step (a);

f. passing a portion of said regenerated catalyst formed in step (d)into said second reaction zone; and,

g. withdrawing spent catalyst from the bottom of said first reactionzone.

4. A process for the catalytic hydroprocessing of hydrocarbonscontaining metal, sulfur and nitrogen impurities therein, said processusing at least two movingbed reactors operated in series hydrocarbonflow, which comprises the steps of:

a. passing a hydrocarbon charge stock and hydrogen through a firstmoving-bed reaction zone to contact regenerated catalyst hereinafterdescribed, said catalyst flowing downward in said first reaction zone toremove metal impurities from said charge stock;

b. passing a portion of the reaction effluent from the first reactionzone to the top of a second movingbed reaction zone to contact therein amixture of fresh and regenerated catalyst flowing downward in saidsecond reaction zone to remove sulfur and nitrogen impurities from saideffluent;

cv removing used catalyst from the bottom of said second reaction zone;

d. contacting said used catalyst with an oxygencontaining gas to burnoff accumulated carbon deposits to form regenerated catalyst in aregeneration zone;

e. passing a portion of said regenerated catalyst formed in step (d)into said first reaction zone as said regenerated catalyst of step (a);

f. passing a portion of said regenerated catalyst formed in step ((1)into said second reaction zone; and,

g. withdrawing said regenerated catalyst containing said metalimpurities from the bottom of said first reaction zone.

1. A PROCESS FOR THE CATALYTIC HYDROPROCESSING OF HYDROCARBONSCONTAINING METAL, SULFUR AND NITROGEN IMPURITIES THEREIN, SAID PROCESSHAVING AT LEAST TWO MOVING-BED REACTORS OPERATE WITH SERIES HYDROCARBONFLOW WHICH COMPRISES THE STEPS OF: A. PASSING A HYDROCARBON CHARGE STOCKAND HYDROGEN THROUGH A FIRST MOVING-BED REACTION ZONE TO CONTACTREGENERATED CATALYST HEREINAFTER DESCRIBED, SAID CATALYST FLOWINGDOWNWARD IN SAID FIRST REACTION ZONE TO REMOVE METAL IMPURITIES FROMSAID CHARGE STOCK, B. PASSING A PORTION OF THE REACTION EFFUENT FROM THEFIRST REACTION ZONE TO THE TOP OF A SECOND MOVING-BED REACTION ZONE TOCONTAFCT THEREIN FRESH CATALYST FLOWING DOWNWARD IN SAID SECOND REACTIONZONE TO REMOVE SULFUR AND NITRO-15 GEN IMPURITIES FROM SAID EFFUENT, C.REMOVING USED CATALYST FROM THE BOTTOM OF SAID SECOND REACTION ZONE, D.CONTACTING SAID USED CATALYST WITH AN OXYGEN-CONTAINING GAS IN AREGENERATION ZONE TO BURN OFF ACCUMULATED CAR-30 BON DEPOSITS TO FORMREGENERATED CATALYST, E. PASSING REGENERATED CATALYST FORMED IN STEP (D)INTO SAID FIRST REACTION ZONE AS SAID REGENERATED CATALYST OF STEP (A),AND, F. WITHDRAWING SAID REGENERATED CAFTALYST CONTAINING SAID METALIMPURITIES FROM THE BOTTOM OF SAID FIRST REACTION ZONE.
 2. A process forthe catalytic hydroprocessing of hydrocarbons containing metal, sulfurand nitrogen impurities therein, said process having at least twomoving-bed reactors operated with series hydrocarbon flow whichcomprises the steps of: a. passing a hydrocarbon charge stock andhydrogen through a first moving-bed reaction zone to contact regeneratedcatalyst hereinafter described, said catalyst flowing downward in saidfirst reaction zone to remove metal impurities from said charge stock;b. passing a portion of the reaction effluent from the first reactionzone to the top of a second moving-bed reaction zone to contact thereinfresh catalyst flowing downward in said second reaction zone to removesulfur and nitrogen impurities from said effluent; c. removing usedcatalyst from the bottom of said second reaction zone; d. contactingsaid used catalyst with an oxygen-containing gas in a regeneration zoneto burn off accumulated carbon deposits to form regenerated catalyst; e.passing regenerated catalyst formed in step (d) into said first reactionzone as said regenerated catalyst of step (a); and, f. withdrawing spentcatalyst from the bottom of said first reaction zone.
 3. A process forthe catalytic hydroprocessing of hydrocarbons containing metal, sulfurand nitrogen impurities therein, said process using at least twomoving-bed reactors operated in series hydrocarbon flow, which comprisesthe steps of: a. passing a hydrocarbon charge stock and hydrogen througha first moving-bed reaction zone to contact regenerated catalysthereinafter described, said catalyst flowing downward in said firstreaction zone to remove metal impurities from said charge stock; b.passing a portion of the reaction effluent from the first reaction zoneto the top of a second moving-bed reaction zone to contact therein amixture of fresh and regenerated catalyst flowing downward in saidsecond reaction zone to remove sulfur and nitrogen impurities from saideffluent; c. removing used catalyst from the bottom of said secondreaction zone; d. contacting said used catalyst with anoxygen-containing gas to burn off accumulated carbon deposits to formregenerated catalyst in a regeneration zone; e. passing a portion ofsaid regenerated catalyst formed in step (d) into said first reactionzone as said regenerated catalyst of step (a); f. passing a portion ofsaid regenerated catalyst formed in step (d) into said second reactionzone; and, g. withdrawing spent catalyst from the bottom of said firstreaction zone.
 4. A process for the catalytic hydroprocessing ofhydrocarbons containing metal, sulfur and nitrogen impurities therein,said process using at least two moving-bed reactors operated in serieshydrocarbon flow, which comprises the steps of: a. passing a hydrocarboncharge stock and hydrogen through a first moving-bed reaction zone tocontact regenerated catalyst hereinafter described, said catalystflowing downward in said first reaction zone to remove metal impuritiesfrom said charge stock; b. passing a portion of the reaction effluentfrom the first reaction zone to the top of a second moving-bed reactionzone to contact therein a mixture of fresh and regenerated catalystflowing downward in said second reaction zone to remove sulfur andnitrogen impurities from said effluent; c. removing used catalyst fromthe bottom of said second reaction zone; d. contacting said usedcatalyst with an oxygen-containing gas to burn off accumulated carbondeposits to form regenerated catalyst in a regeneration zone; e. passinga portion of said regenerated catalyst formed in step (d) into saidfirst reaction zone as said regenerated catalyst of step (a); f. passinga portion of said regenerated catalyst formed in step (d) into saidsecond reaction zone; and, g. withdrawing said regenerated catalystcontaining said metal impurities from the bottom of said first reactionzone.